In air blast circuit-breaker installations, high-pressure air tanks are used in which the air is compressed by compressors which communicate via discharge units to high-pressure tanks which feed the circuit-breakers. To prevent ingress of impurities and more particularly of dampness in the cut-out chambers of the circuit-breakers, the high-pressure tanks are provided with drainage devices. Known devices of this type are constituted by controllable valves disposed at the bottom of the tanks.
Known drainage devices have the disadvantage of requiring high air consumption e.g. several cubic meters, the valve opening time frequently being a few seconds. Such air consumption requires an appreciable increase in the operation time of the compressors.
The present invention aims to mitigate said disadvantage and to produce a drainage device which considerably reduces air consumption.